[PATCH v3 2/2] thunderbolt: Add device links for Apple T2 NHI

[Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>]

From: Andre Eikmeyer <andre@negmaster.com>

Thunderbolt NHI on T2 Macs (2018-2020). The NHI and its
associated PCIe root ports all sit directly on the root complex
with no upstream port. Apple's ACPI tables name Thunderbolt root
ports as TRP0, TRP1, etc. Find them and create device links back
to the NHI so that PCIe tunnels can be re-established after sleep.

Co-developed-by: Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>
Signed-off-by: Atharva Tiwari <atharvatiwarilinuxdev@gmail.com>

Signed-off-by: Andre Eikmeyer <andre@negmaster.com>
---
 drivers/thunderbolt/tb.c | 51 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 50 insertions(+), 1 deletion(-)

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index c69c323e6952..0cdffcf577cd 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2019, Intel Corporation
  */
 
+#include <linux/acpi.h>
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/delay.h>
@@ -3305,11 +3306,59 @@ static const struct tb_cm_ops tb_cm_ops = {
 static bool tb_apple_add_links(struct tb_nhi *nhi)
 {
 	struct pci_dev *upstream, *pdev;
-	bool ret;
+	bool ret = false;
 
 	if (!x86_apple_machine)
 		return false;
 
+	/* On T2 Macs. the root ports are stored in ACPI as TRP0,
+	 * TRP1, etc. Find them and create device links
+	 * so that PCIe tunnels can be re-established after
+	 * sleep.
+	 */
+	if (has_apple_t2_chip && IS_ENABLED(CONFIG_ACPI)) {
+		struct acpi_device *adev;
+		unsigned int slot, func;
+		const struct device_link *link;
+		const char *bid;
+
+		for (slot = 0; slot < 32; slot++) {
+			for (func = 0; func < 8; func++) {
+				pdev = pci_get_slot(nhi->pdev->bus, PCI_DEVFN(slot, func));
+				if (!pdev)
+					continue;
+
+				if (!pci_is_pcie(pdev) || pci_pcie_type(pdev) !=
+						PCI_EXP_TYPE_ROOT_PORT)
+					goto put_pdev;
+
+				adev = ACPI_COMPANION(&pdev->dev);
+				if (!adev)
+					goto put_pdev;
+
+				bid = acpi_device_bid(adev);
+				if (strncmp(bid, "TRP", 3) != 0)
+					goto put_pdev;
+
+				link = device_link_add(&pdev->dev, &nhi->pdev->dev,
+						DL_FLAG_AUTOREMOVE_SUPPLIER |
+						DL_FLAG_PM_RUNTIME);
+				if (link) {
+					dev_dbg(&nhi->pdev->dev, "created link from %s\n",
+						dev_name(&pdev->dev));
+					ret = true;
+				} else
+					dev_warn(&nhi->pdev->dev,
+						"device link creation from %s failed\n",
+						dev_name(&pdev->dev));
+
+put_pdev:
+	pci_dev_put(pdev);
+			}
+		}
+		return ret;
+	}
+
 	switch (nhi->pdev->device) {
 	case PCI_DEVICE_ID_INTEL_LIGHT_RIDGE:
 	case PCI_DEVICE_ID_INTEL_CACTUS_RIDGE_4C:
-- 
2.43.0